This invention relates to the field of pumps and, in particular, to liquid level maintaining pumps with automatic activation and deactivation arrangements.
Liquid pumps, such as bilge and sump pumps, are employed in liquid level maintaining systems, frequently as safety equipment in many structures, such as in watercraft and homes. Pumps in liquid level maintaining systems may also be used in other applications, such as maintaining liquid levels in tanks or reservoirs between predetermined minimum and maximum levels. The bilge and sump pump systems generally try to keep the water level inside the structure to a minimum to lesson or eliminate damage to the structure by the water. Some known systems utilize a water level detecting apparatus to activate and deactivate the pump motor. When the detecting apparatus determines that the water level has reached a predetermined maximum level, the pump motor is activated. When the detecting mechanism determines that the water level has dropped below a predetermined minimum level, the pump motor is deactivated. In some systems, the same level is used for both the maximum and minimum.
There are generally two types of liquid level detecting apparatus used in these systems, an xe2x80x9copen detector devicexe2x80x9d and a xe2x80x9cclosed detector device.xe2x80x9d The open detector device utilizes the presence of an outside conductive material between two electric terminals to complete an electrical path through the conductive material between the two terminals in order to switch on and off the detecting circuitry of the system. That is, when an external conductive material, such as, for example water, enters the open detector device and comes into electrical contact with the detecting circuitry terminals and completes the electric circuit, the open detector device circuitry causes activation or deactivation of the pump. The detection of the liquid will generally result in activation of the pump, but it could also result in deactivation. Sometimes a combination of three or more terminals are used in the open detection device.
The closed detector device, by contrast, does not require the presence of an outside conductive material to complete an electrical path in order to activate detecting circuitry within the device. That is, all necessary electrical components are included within a closed detector device system.
A bilge pump utilizing a closed detector device is disclosed in U.S. Pat. No. 3,717,420 (Rachocki). The pump disclosed in Rachocki utilizes a float mechanism to detect the water level within a vessel. The float mechanism includes a magnet. As the water level rises, the float rises to a point where the magnetic field of the magnet causes a reed switch to close. When the switch is closed, the pump motor is activated and water is pumped out of the vessel. When the water level drops, the float drops activating a thermostatic delay mechanism. After a delay, the magnetic field is removed from the reed switch, the switch opens and the pump motor is deactivated. One drawback of the bilge pump disclosed in Rachocki is that pump is subject to variation due to the reliance on temperature of the delay mechanism.
A sump pump drive system using a closed detector device is disclosed in U.S. Pat. No. 5,234,319 (Wilder). The sump pump drive system also uses a float to detect water levels. The float is placed in a signal-producing relationship with an analog signal generator. When the water level rises, the float rises and the signal generator causes the pump motor to cycle. This system, however, suffers some drawbacks. That is, since the system uses a single float mechanism to activate and deactivate the pump, the pump motor would undergo cycling due to minor fluctuations in the water level.
U.S. Pat. Nos. 5,562,423 and 5,297,939 (both Orth et al.) refer to an automatic control mechanism for bilge and sump pumps. The automatic control mechanism disclosed in these patents is a closed detector device consisting of a float, a magnet affixed to the float, and a reed switch. A top portion of the chamber encasing the float and magnet is provided with a one-way valve which allows air to exit, but not enter, the chamber. As water enters the lower portion of the chamber, the float and magnet rise and the reed switch is eventually closed. Air exits through the one-way valve, and as the water level drops, a partial vacuum is created above the magnet in the top portion of the chamber. The partial vacuum prevents the magnet from dropping along with the water. When the water level drops below an air inlet contained within the lower portion of the chamber, air enters the chamber and the magnet drops, allowing the motor to be deactivated. One problem is that the automatic control mechanism is only as reliable as the partial vacuum created. Thus, if the vacuum created is insufficient, the magnet will drop along with the water, causing cycling of the pump motor. If the vacuum is too strong, the magnet may not drop, causing continued running of the pump motor.
U.S. Pat. Nos. 5,078,577 (Heckman), 4,678,403 (Rudy et al), 4,171,932 (Miller) and 4,205,237 (Miller) refer to liquid pumps using an open detector device consisting of conductance sensors to detect the water level, and hence, activate or deactivate the pump. The sensors are placed at a high water level. When the water reaches the high water level and comes into contact with the sensors, a conduction path is created between the sensors allowing current sensing circuitry to activate the pump motor. When the water drops below the high water level, the conduction path is removed and the pump is deactivated. There are drawbacks to these systems. These systems rely on sensors that must be immersed in water to operate the pump. The sensors used may become dirty, corroded or even broken, affecting the conductance of the sensors. In addition, the water may contain a material affecting the conductance of the water which could also prevent the pump from being activated.
U.S. Pat. No. 4,265,262 (Hotine) refers to a pump control system for a reservoir tank utilizing an open detector device to detect the level of water in the reservoir. The system uses a pair of conductance sensing probes at a high water level and a pair of conductance sensing probes at a low water level. The reservoir pump is activated when water reaches the pair of conductance sensors located at the high water level and deactivated when the water drops below the pair of conductance sensors located at the low water level. U.S. Pat. No. 4,766,329 (Santiago) also refers to a pump control system utilizing an open detector device to detect high and low water levels. Three probes are arranged in a staggered pattern such that there is one probe at the high water level, a second probe at the low water level and a third probe located below the low water level. When water rises to the high water probe, all three probes are in contact with the water and a conduction path is created which energizes a relay to activate the pump. As the level of the water drops, a conductance path is created between the low water probe and the third probe which energizes a holding circuit to maintain the operation of the pump. When the level of the water drops below the low water probe, the conductance path is removed and the pump is deactivated. These systems, however, like the ones described above, rely on probes that must be immersed in salt water to operate the pump. The probes used may become dirty, corroded or even broken, affecting the conductance of the probes. In addition, the water may contain a material affecting the conductance of the water which could also prevent the pump from being activated.
U.S. Pat. Nos. 5,076,763, 5,324,170 and 5,545,012 (all to Anastos et al.) refer to closed detector devices using a timer and an electrical condition sensor to activate and deactivate a bilge pump motor. At predetermined intervals, the timer sends a signal to activate the pump motor. Once activated, the condition sensor ascertains the load on the motor, which is an indicator of the amount of physical resistance being experienced at the pump""s impellers due to the presence or absence of water. If the presence of water is detected, the pump remains on to pump out the water. However, if the presence of water is not detected, the pump is shut off. The ""012 patent includes the use of a periodic duty cycle generator, which includes a timer and a generator. The timer actuates the generator at a predetermined cycle, and the generator sends a signal to the motor to operate at a fraction of its full power (so the motor will be less noisy). Once activated, the condition sensor ascertains the load on the motor as described above. U.S. Pat. No. 4,841,404 (Marshall et al.) also uses a load sensor to deactivate an operating pump. These pumps, however, have some drawbacks. First, in order to sense the load on the motor, the motor must be turned on. The cycling of the motor creates noise, which may not be desirable, particularly at night. In addition, the use of timers to activate the pump may be less efficient than a mechanism which acts upon sensed information to maintain the water level, since a timer cannot take into account a change in condition such as, for example, a massive influx of water.
The aforementioned detection mechanisms utilize different xe2x80x9cdetection criteriaxe2x80x9d to determine activation and deactivation water levels. These criteria include, but are not limited to sensing the load on an operating motor, detecting the level of a water using a float to trigger a reed switch and sensing a conductance path through water.
There is a need and desire for a liquid pump that utilizes water level detection mechanisms to activate and deactivate the pump that will lessen cycling of the pump motor. The liquid pump detection mechanisms should also withstand the extreme environment of a vessel""s bilge and, in particular, the corrosion problems attributable to water. The liquid pump detection mechanisms should sense the level of the water residing in a vessel""s bilge to take into account a change in water condition such as, for example, a massive influx of water.
The disadvantages of the prior art are overcome to a great extent by the present invention, which in one embodiment provides a pump with separate pump activation and deactivation mechanisms that are both closed detector devices. The pump activation mechanism includes a float device that activates the pump motor when water within the pump housing reaches a high water level. The pump deactivation mechanism includes a sensor that detects the load on the pump motor and deactivates it when the sensed load indicates that the water within the pump housing has reached a low water level.
In another aspect of the invention, a pump with separate activation and deactivation mechanism is provided. The activation and deactivation mechanisms use different detecting criteria to determine activation and deactivation water levels.
In another aspect, a control circuit for a liquid pump includes an activation circuit and a pump deactivation circuit. The circuits are coupled to a trigger circuit which operates an activation switch for the pump. The activation circuit generates an activation signal when the liquid reaches the first level and the pump deactivation circuit generates a deactivation signal when the liquid reaches a second level. The trigger circuit closes and opens the activation switch to activate and deactivate the pump responsive to the activation and deactivation signals.
In yet another aspect of the invention, a floating apparatus for detecting a level of water includes a float assembly and a float compartment. The float compartment includes an inner surface and is slightly larger than the float assembly. The float assembly is disposed within said inner surface. The compartment contains a first wall with an opening to allow liquid to enter the compartment and the float assembly rises with a level of the liquid and is guided by the inner surface.
In yet another aspect of the invention, a method of controlling a pump adapted to pump liquid comprises: providing a first closed detector device, said first closed detector device determining when the liquid has reached the first level; activating the pump when the first closed detector device indicates that the liquid has reached the first level; providing a second closed detector device, said second closed detector device determining when the liquid has reached a second level by sensing an electrical condition of the activated pump; and deactivating the pump when the second closed detector device has detected an electrical condition indicating that the liquid has dropped to a second level.
In still a further aspect of the invention, a method of controlling a pump adapted to pump liquid comprises: providing a first closed detector device, said first closed detector device determining when the liquid has reached the first level; activating the pump when the first closed detector device indicates that the liquid has reached the first level; providing a second closed detector device, said second closed detector device determining when the liquid has reached a second level; and deactivating the pump when the second closed detector device has detected that the liquid has dropped to a second level.
It is an object of the invention to provide a pump and a controller for a liquid level maintaining system.
It is a further object of the invention to provide a pump and controller for a liquid level maintaining system with an activation mechanism and a separate deactivation mechanism.
It is a further object of the invention to provide a pump and a controller with an activation mechanism and a separate deactivation mechanism using different criteria to detect different water levels.
It is yet another object of the present invention to provide a pump and a controller with separate mechanisms to activate and deactivate the pump that will lessen the cycling of the pump""s motor.
It is still another object of the present invention to provide a pump and controller with separate mechanisms to activate and deactivate the pump that will withstand the extreme environment of a vessel""s bilge and, in particular, the corrosion problems attributable to water.
It is still a further object of the present invention to provide a pump and controller with separate mechanisms to activate and deactivate the pump that senses the level of the water residing in a vessel""s bilge to take into account changes in the water level.
Other objects, features and advantages of the present invention will become apparent from the following detailed description and drawings of preferred embodiments of the present invention.